The Oxford Thesaurus An A-Z Dictionary of Synonyms - undercurrentn.

1) undertow, cross-current, rip tide, rip (current) , underflow: Caught in the undercurrent, he was carried out to sea. 2) undertone, subcurrent, trend, tendency, overtone, tenor, suggestion, murmur, implication, connotation, sense, feeling, aura, tinge, flavour, atmosphere, ambience or ambiance; vibrations, Colloq vibes: There is a sinister undercurrent of gloom about this place.